Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.81
1.81 ! markus 1: .\" $OpenBSD: ssh-keygen.1,v 1.80 2009/10/24 00:48:34 dtucker Exp $
1.29 niklas 2: .\"
1.1 deraadt 3: .\" -*- nroff -*-
4: .\"
5: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
6: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
7: .\" All rights reserved
8: .\"
1.22 deraadt 9: .\" As far as I am concerned, the code I have written for this software
10: .\" can be used freely for any purpose. Any derived versions of this
11: .\" software must be clearly marked as such, and if the derived work is
12: .\" incompatible with the protocol description in the RFC file, it must be
13: .\" called by a name other than "ssh" or "Secure Shell".
14: .\"
15: .\"
1.33 deraadt 16: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
17: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
18: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
1.22 deraadt 19: .\"
20: .\" Redistribution and use in source and binary forms, with or without
21: .\" modification, are permitted provided that the following conditions
22: .\" are met:
23: .\" 1. Redistributions of source code must retain the above copyright
24: .\" notice, this list of conditions and the following disclaimer.
25: .\" 2. Redistributions in binary form must reproduce the above copyright
26: .\" notice, this list of conditions and the following disclaimer in the
27: .\" documentation and/or other materials provided with the distribution.
1.1 deraadt 28: .\"
1.22 deraadt 29: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
30: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
31: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
32: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
33: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
34: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
38: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 deraadt 39: .\"
1.81 ! markus 40: .Dd $Mdocdate: October 24 2009 $
1.2 deraadt 41: .Dt SSH-KEYGEN 1
42: .Os
43: .Sh NAME
44: .Nm ssh-keygen
1.37 markus 45: .Nd authentication key generation, management and conversion
1.2 deraadt 46: .Sh SYNOPSIS
47: .Nm ssh-keygen
1.56 jmc 48: .Bk -words
1.25 markus 49: .Op Fl q
1.2 deraadt 50: .Op Fl b Ar bits
1.53 stevesk 51: .Fl t Ar type
1.2 deraadt 52: .Op Fl N Ar new_passphrase
53: .Op Fl C Ar comment
1.20 markus 54: .Op Fl f Ar output_keyfile
1.56 jmc 55: .Ek
1.2 deraadt 56: .Nm ssh-keygen
57: .Fl p
58: .Op Fl P Ar old_passphrase
59: .Op Fl N Ar new_passphrase
1.9 markus 60: .Op Fl f Ar keyfile
1.2 deraadt 61: .Nm ssh-keygen
1.37 markus 62: .Fl i
1.20 markus 63: .Op Fl f Ar input_keyfile
1.16 deraadt 64: .Nm ssh-keygen
1.37 markus 65: .Fl e
1.20 markus 66: .Op Fl f Ar input_keyfile
1.16 deraadt 67: .Nm ssh-keygen
1.17 markus 68: .Fl y
1.20 markus 69: .Op Fl f Ar input_keyfile
1.17 markus 70: .Nm ssh-keygen
1.2 deraadt 71: .Fl c
72: .Op Fl P Ar passphrase
73: .Op Fl C Ar comment
1.9 markus 74: .Op Fl f Ar keyfile
75: .Nm ssh-keygen
76: .Fl l
1.35 markus 77: .Op Fl f Ar input_keyfile
78: .Nm ssh-keygen
79: .Fl B
1.20 markus 80: .Op Fl f Ar input_keyfile
1.48 jakob 81: .Nm ssh-keygen
82: .Fl D Ar reader
83: .Nm ssh-keygen
1.64 djm 84: .Fl F Ar hostname
85: .Op Fl f Ar known_hosts_file
1.79 sthen 86: .Op Fl l
1.64 djm 87: .Nm ssh-keygen
88: .Fl H
89: .Op Fl f Ar known_hosts_file
90: .Nm ssh-keygen
91: .Fl R Ar hostname
92: .Op Fl f Ar known_hosts_file
93: .Nm ssh-keygen
1.48 jakob 94: .Fl U Ar reader
95: .Op Fl f Ar input_keyfile
1.57 jakob 96: .Nm ssh-keygen
97: .Fl r Ar hostname
98: .Op Fl f Ar input_keyfile
99: .Op Fl g
1.60 djm 100: .Nm ssh-keygen
101: .Fl G Ar output_file
1.61 djm 102: .Op Fl v
1.60 djm 103: .Op Fl b Ar bits
104: .Op Fl M Ar memory
105: .Op Fl S Ar start_point
106: .Nm ssh-keygen
107: .Fl T Ar output_file
108: .Fl f Ar input_file
1.61 djm 109: .Op Fl v
1.60 djm 110: .Op Fl a Ar num_trials
111: .Op Fl W Ar generator
1.13 aaron 112: .Sh DESCRIPTION
1.2 deraadt 113: .Nm
1.37 markus 114: generates, manages and converts authentication keys for
1.2 deraadt 115: .Xr ssh 1 .
1.15 deraadt 116: .Nm
1.54 deraadt 117: can create RSA keys for use by SSH protocol version 1 and RSA or DSA
1.58 jmc 118: keys for use by SSH protocol version 2.
119: The type of key to be generated is specified with the
1.25 markus 120: .Fl t
1.52 djm 121: option.
1.70 djm 122: If invoked without any arguments,
123: .Nm
1.71 jmc 124: will generate an RSA key for use in SSH protocol 2 connections.
1.15 deraadt 125: .Pp
1.60 djm 126: .Nm
127: is also used to generate groups for use in Diffie-Hellman group
128: exchange (DH-GEX).
129: See the
130: .Sx MODULI GENERATION
131: section for details.
132: .Pp
1.2 deraadt 133: Normally each user wishing to use SSH
1.15 deraadt 134: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 135: key in
1.68 djm 136: .Pa ~/.ssh/identity ,
137: .Pa ~/.ssh/id_dsa
1.15 deraadt 138: or
1.68 djm 139: .Pa ~/.ssh/id_rsa .
1.15 deraadt 140: Additionally, the system administrator may use this to generate host keys,
141: as seen in
142: .Pa /etc/rc .
1.2 deraadt 143: .Pp
1.1 deraadt 144: Normally this program generates the key and asks for a file in which
1.12 aaron 145: to store the private key.
146: The public key is stored in a file with the same name but
1.2 deraadt 147: .Dq .pub
1.12 aaron 148: appended.
149: The program also asks for a passphrase.
150: The passphrase may be empty to indicate no passphrase
1.26 markus 151: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 152: arbitrary length.
1.51 stevesk 153: A passphrase is similar to a password, except it can be a phrase with a
154: series of words, punctuation, numbers, whitespace, or any string of
155: characters you want.
156: Good passphrases are 10-30 characters long, are
1.1 deraadt 157: not simple sentences or otherwise easily guessable (English
1.42 markus 158: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 159: passphrases), and contain a mix of upper and lowercase letters,
160: numbers, and non-alphanumeric characters.
1.12 aaron 161: The passphrase can be changed later by using the
1.2 deraadt 162: .Fl p
1.1 deraadt 163: option.
1.2 deraadt 164: .Pp
1.12 aaron 165: There is no way to recover a lost passphrase.
166: If the passphrase is
1.49 deraadt 167: lost or forgotten, a new key must be generated and copied to the
1.1 deraadt 168: corresponding public key to other machines.
1.2 deraadt 169: .Pp
1.37 markus 170: For RSA1 keys,
171: there is also a comment field in the key file that is only for
1.12 aaron 172: convenience to the user to help identify the key.
173: The comment can tell what the key is for, or whatever is useful.
174: The comment is initialized to
1.2 deraadt 175: .Dq user@host
176: when the key is created, but can be changed using the
177: .Fl c
1.1 deraadt 178: option.
1.2 deraadt 179: .Pp
1.15 deraadt 180: After a key is generated, instructions below detail where the keys
181: should be placed to be activated.
182: .Pp
1.2 deraadt 183: The options are as follows:
184: .Bl -tag -width Ds
1.60 djm 185: .It Fl a Ar trials
186: Specifies the number of primality tests to perform when screening DH-GEX
187: candidates using the
188: .Fl T
189: command.
1.66 jmc 190: .It Fl B
191: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 192: .It Fl b Ar bits
1.12 aaron 193: Specifies the number of bits in the key to create.
1.72 dtucker 194: For RSA keys, the minimum size is 768 bits and the default is 2048 bits.
1.69 djm 195: Generally, 2048 bits is considered sufficient.
1.72 dtucker 196: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.66 jmc 197: .It Fl C Ar comment
198: Provides a new comment.
1.2 deraadt 199: .It Fl c
1.1 deraadt 200: Requests changing the comment in the private and public key files.
1.50 markus 201: This operation is only supported for RSA1 keys.
1.1 deraadt 202: The program will prompt for the file containing the private keys, for
1.41 stevesk 203: the passphrase if the key has one, and for the new comment.
1.81 ! markus 204: .It Fl D Ar pkcs11
! 205: Download the RSA public keys stored in the
! 206: .Ar pkcs11
! 207: provider.
1.37 markus 208: .It Fl e
1.40 markus 209: This option will read a private or public OpenSSH key file and
1.73 markus 210: print the key in
211: RFC 4716 SSH Public Key File Format
1.37 markus 212: to stdout.
213: This option allows exporting keys for use by several commercial
214: SSH implementations.
1.66 jmc 215: .It Fl F Ar hostname
216: Search for the specified
217: .Ar hostname
218: in a
219: .Pa known_hosts
220: file, listing any occurrences found.
221: This option is useful to find hashed host names or addresses and may also be
222: used in conjunction with the
223: .Fl H
224: option to print found keys in a hashed format.
225: .It Fl f Ar filename
226: Specifies the filename of the key file.
227: .It Fl G Ar output_file
228: Generate candidate primes for DH-GEX.
229: These primes must be screened for
230: safety (using the
231: .Fl T
232: option) before use.
1.57 jakob 233: .It Fl g
1.62 jakob 234: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 235: .Fl r
1.62 jakob 236: command.
1.66 jmc 237: .It Fl H
238: Hash a
239: .Pa known_hosts
1.67 dtucker 240: file.
241: This replaces all hostnames and addresses with hashed representations
242: within the specified file; the original content is moved to a file with
243: a .old suffix.
1.66 jmc 244: These hashes may be used normally by
245: .Nm ssh
246: and
247: .Nm sshd ,
248: but they do not reveal identifying information should the file's contents
249: be disclosed.
250: This option will not modify existing hashed hostnames and is therefore safe
251: to use on files that mix hashed and non-hashed names.
1.37 markus 252: .It Fl i
253: This option will read an unencrypted private (or public) key file
254: in SSH2-compatible format and print an OpenSSH compatible private
255: (or public) key to stdout.
256: .Nm
1.38 markus 257: also reads the
1.74 jmc 258: RFC 4716 SSH Public Key File Format.
1.37 markus 259: This option allows importing keys from several commercial
260: SSH implementations.
1.9 markus 261: .It Fl l
1.77 grunk 262: Show fingerprint of specified public key file.
1.50 markus 263: Private RSA1 keys are also supported.
264: For RSA and DSA keys
265: .Nm
1.78 jmc 266: tries to find the matching public key file and prints its fingerprint.
267: If combined with
268: .Fl v ,
269: an ASCII art representation of the key is supplied with the fingerprint.
1.66 jmc 270: .It Fl M Ar memory
271: Specify the amount of memory to use (in megabytes) when generating
272: candidate moduli for DH-GEX.
273: .It Fl N Ar new_passphrase
274: Provides the new passphrase.
275: .It Fl P Ar passphrase
276: Provides the (old) passphrase.
1.2 deraadt 277: .It Fl p
1.1 deraadt 278: Requests changing the passphrase of a private key file instead of
1.12 aaron 279: creating a new private key.
280: The program will prompt for the file
1.1 deraadt 281: containing the private key, for the old passphrase, and twice for the
282: new passphrase.
1.5 aaron 283: .It Fl q
284: Silence
285: .Nm ssh-keygen .
286: Used by
287: .Pa /etc/rc
288: when creating a new key.
1.64 djm 289: .It Fl R Ar hostname
290: Removes all keys belonging to
291: .Ar hostname
1.65 jmc 292: from a
1.64 djm 293: .Pa known_hosts
294: file.
1.65 jmc 295: This option is useful to delete hashed hosts (see the
1.64 djm 296: .Fl H
297: option above).
1.66 jmc 298: .It Fl r Ar hostname
299: Print the SSHFP fingerprint resource record named
300: .Ar hostname
301: for the specified public key file.
1.60 djm 302: .It Fl S Ar start
303: Specify start point (in hex) when generating candidate moduli for DH-GEX.
304: .It Fl T Ar output_file
305: Test DH group exchange candidate primes (generated using the
306: .Fl G
307: option) for safety.
1.66 jmc 308: .It Fl t Ar type
309: Specifies the type of key to create.
310: The possible values are
311: .Dq rsa1
312: for protocol version 1 and
313: .Dq rsa
314: or
315: .Dq dsa
316: for protocol version 2.
1.61 djm 317: .It Fl v
318: Verbose mode.
319: Causes
320: .Nm
321: to print debugging messages about its progress.
322: This is helpful for debugging moduli generation.
323: Multiple
324: .Fl v
325: options increase the verbosity.
326: The maximum is 3.
1.66 jmc 327: .It Fl W Ar generator
328: Specify desired generator when testing candidate moduli for DH-GEX.
329: .It Fl y
330: This option will read a private
331: OpenSSH format file and print an OpenSSH public key to stdout.
1.2 deraadt 332: .El
1.60 djm 333: .Sh MODULI GENERATION
334: .Nm
335: may be used to generate groups for the Diffie-Hellman Group Exchange
336: (DH-GEX) protocol.
337: Generating these groups is a two-step process: first, candidate
338: primes are generated using a fast, but memory intensive process.
339: These candidate primes are then tested for suitability (a CPU-intensive
340: process).
341: .Pp
342: Generation of primes is performed using the
343: .Fl G
344: option.
345: The desired length of the primes may be specified by the
346: .Fl b
347: option.
348: For example:
349: .Pp
1.66 jmc 350: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 351: .Pp
352: By default, the search for primes begins at a random point in the
353: desired length range.
354: This may be overridden using the
355: .Fl S
356: option, which specifies a different start point (in hex).
357: .Pp
358: Once a set of candidates have been generated, they must be tested for
359: suitability.
360: This may be performed using the
361: .Fl T
362: option.
363: In this mode
364: .Nm
365: will read candidates from standard input (or a file specified using the
366: .Fl f
367: option).
368: For example:
369: .Pp
1.66 jmc 370: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 371: .Pp
372: By default, each candidate will be subjected to 100 primality tests.
373: This may be overridden using the
374: .Fl a
375: option.
376: The DH generator value will be chosen automatically for the
377: prime under consideration.
378: If a specific generator is desired, it may be requested using the
379: .Fl W
380: option.
1.66 jmc 381: Valid generator values are 2, 3, and 5.
1.60 djm 382: .Pp
383: Screened DH groups may be installed in
384: .Pa /etc/moduli .
385: It is important that this file contains moduli of a range of bit lengths and
386: that both ends of a connection share common moduli.
1.2 deraadt 387: .Sh FILES
388: .Bl -tag -width Ds
1.68 djm 389: .It Pa ~/.ssh/identity
1.36 itojun 390: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 391: This file should not be readable by anyone but the user.
392: It is possible to
1.1 deraadt 393: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 394: used to encrypt the private part of this file using 128-bit AES.
1.12 aaron 395: This file is not automatically accessed by
1.2 deraadt 396: .Nm
1.1 deraadt 397: but it is offered as the default file for the private key.
1.46 markus 398: .Xr ssh 1
1.15 deraadt 399: will read this file when a login attempt is made.
1.68 djm 400: .It Pa ~/.ssh/identity.pub
1.36 itojun 401: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 402: The contents of this file should be added to
1.68 djm 403: .Pa ~/.ssh/authorized_keys
1.2 deraadt 404: on all machines
1.49 deraadt 405: where the user wishes to log in using RSA authentication.
1.15 deraadt 406: There is no need to keep the contents of this file secret.
1.68 djm 407: .It Pa ~/.ssh/id_dsa
1.36 itojun 408: Contains the protocol version 2 DSA authentication identity of the user.
1.15 deraadt 409: This file should not be readable by anyone but the user.
410: It is possible to
411: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 412: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 413: This file is not automatically accessed by
414: .Nm
415: but it is offered as the default file for the private key.
1.46 markus 416: .Xr ssh 1
1.15 deraadt 417: will read this file when a login attempt is made.
1.68 djm 418: .It Pa ~/.ssh/id_dsa.pub
1.36 itojun 419: Contains the protocol version 2 DSA public key for authentication.
420: The contents of this file should be added to
1.68 djm 421: .Pa ~/.ssh/authorized_keys
1.36 itojun 422: on all machines
1.49 deraadt 423: where the user wishes to log in using public key authentication.
1.36 itojun 424: There is no need to keep the contents of this file secret.
1.68 djm 425: .It Pa ~/.ssh/id_rsa
1.36 itojun 426: Contains the protocol version 2 RSA authentication identity of the user.
427: This file should not be readable by anyone but the user.
428: It is possible to
429: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 430: used to encrypt the private part of this file using 128-bit AES.
1.36 itojun 431: This file is not automatically accessed by
432: .Nm
433: but it is offered as the default file for the private key.
1.46 markus 434: .Xr ssh 1
1.36 itojun 435: will read this file when a login attempt is made.
1.68 djm 436: .It Pa ~/.ssh/id_rsa.pub
1.36 itojun 437: Contains the protocol version 2 RSA public key for authentication.
1.15 deraadt 438: The contents of this file should be added to
1.68 djm 439: .Pa ~/.ssh/authorized_keys
1.15 deraadt 440: on all machines
1.49 deraadt 441: where the user wishes to log in using public key authentication.
1.12 aaron 442: There is no need to keep the contents of this file secret.
1.60 djm 443: .It Pa /etc/moduli
444: Contains Diffie-Hellman groups used for DH-GEX.
445: The file format is described in
446: .Xr moduli 5 .
1.19 aaron 447: .El
1.2 deraadt 448: .Sh SEE ALSO
449: .Xr ssh 1 ,
450: .Xr ssh-add 1 ,
1.8 ericj 451: .Xr ssh-agent 1 ,
1.60 djm 452: .Xr moduli 5 ,
1.30 itojun 453: .Xr sshd 8
1.37 markus 454: .Rs
1.73 markus 455: .%R RFC 4716
456: .%T "The Secure Shell (SSH) Public Key File Format"
457: .%D 2006
1.37 markus 458: .Re
1.59 jmc 459: .Sh AUTHORS
460: OpenSSH is a derivative of the original and free
461: ssh 1.2.12 release by Tatu Ylonen.
462: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
463: Theo de Raadt and Dug Song
464: removed many bugs, re-added newer features and
465: created OpenSSH.
466: Markus Friedl contributed the support for SSH
467: protocol versions 1.5 and 2.0.
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